1. Field of the Invention
The present invention relates to a data communication apparatus for dividing data such as image data, character code data or the like and then transmitting the divided data and, more particularly, to a data communication apparatus which can efficiently retransmit and correct the data.
2. Related Background Art
Conventional technologies will now be practically described in accordance with the sequence of the items shown below with respect to a facsimile apparatus for executing a communication of an image as such a kind of data communication apparatus.
.sctn.1 Description of a constitution of an HDLC frame (using FIG. 1) PA0 .sctn.2 Practical example of error retransmission using the HDLC frame constitution (using FIG. 2) PA0 .sctn.3 Problems which are caused by error retransmission using the HDLC frame constitution PA0 .sctn.4 Drawbacks of the error retransmission system which has conventionally been known PA0 NSF is a non-standard apparatus signal, PA0 CSI is a called station identifying signal, PA0 DIS is a digital identifying signal, PA0 NSS is a non-standard apparatus setting signal, PA0 TSI is a transmission terminal identifying signal, PA0 DCS is a digital command signal, PA0 TCF is a training check signal, PA0 CFR is a reception preparation confirming signal, PA0 EOP is an end of procedure signal, and PA0 DCN is a disconnection command signal. PA0 (Refer to T. 30 CCITT Recommendation.)
.sctn.3.1 Influences upon line error PA1 .sctn.3.2 Influences due to the bit position where an error occurred (using FIG. 3) PA1 .sctn.3.3 Influences based on the propagation delay characteristic of the communication line (using FIG. 4) PA1 .sctn.3.4 Difficulty in encoding PA1 .sctn.4.1 Regarding fallback PA1 .sctn.4.2 Regarding the process in the case where the reception of a training signal has resulted in a failure (using FIGS. 5 to 7) PA1 .sctn.4.3 Regarding the process in the case where EOL cannot be detected PA1 .sctn.4.4 Regarding the process in the case where the transmission of an image signal has been finished PA1 .sctn.4.5 Regarding the process after an instruction signal of a retransmission start line or the like has been sent PA1 .sctn.4.6 Regarding the selection of the error retransmission mode